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145 lines
4 KiB
C
145 lines
4 KiB
C
#ifndef Py_HASH_H
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#define Py_HASH_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Helpers for hash functions */
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#ifndef Py_LIMITED_API
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PyAPI_FUNC(Py_hash_t) _Py_HashDouble(double);
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PyAPI_FUNC(Py_hash_t) _Py_HashPointer(void*);
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PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t);
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#endif
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/* Prime multiplier used in string and various other hashes. */
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#define _PyHASH_MULTIPLIER 1000003UL /* 0xf4243 */
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/* Parameters used for the numeric hash implementation. See notes for
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_Py_HashDouble in Python/pyhash.c. Numeric hashes are based on
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reduction modulo the prime 2**_PyHASH_BITS - 1. */
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#if SIZEOF_VOID_P >= 8
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# define _PyHASH_BITS 61
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#else
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# define _PyHASH_BITS 31
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#endif
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#define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
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#define _PyHASH_INF 314159
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#define _PyHASH_NAN 0
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#define _PyHASH_IMAG _PyHASH_MULTIPLIER
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/* hash secret
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*
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* memory layout on 64 bit systems
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* cccccccc cccccccc cccccccc uc -- unsigned char[24]
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* pppppppp ssssssss ........ fnv -- two Py_hash_t
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* k0k0k0k0 k1k1k1k1 ........ siphash -- two uint64_t
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* ........ ........ ssssssss djbx33a -- 16 bytes padding + one Py_hash_t
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* ........ ........ eeeeeeee pyexpat XML hash salt
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*
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* memory layout on 32 bit systems
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* cccccccc cccccccc cccccccc uc
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* ppppssss ........ ........ fnv -- two Py_hash_t
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* k0k0k0k0 k1k1k1k1 ........ siphash -- two uint64_t (*)
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* ........ ........ ssss.... djbx33a -- 16 bytes padding + one Py_hash_t
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* ........ ........ eeee.... pyexpat XML hash salt
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*
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* (*) The siphash member may not be available on 32 bit platforms without
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* an unsigned int64 data type.
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*/
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#ifndef Py_LIMITED_API
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typedef union {
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/* ensure 24 bytes */
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unsigned char uc[24];
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/* two Py_hash_t for FNV */
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struct {
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Py_hash_t prefix;
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Py_hash_t suffix;
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} fnv;
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/* two uint64 for SipHash24 */
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struct {
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uint64_t k0;
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uint64_t k1;
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} siphash;
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/* a different (!) Py_hash_t for small string optimization */
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struct {
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unsigned char padding[16];
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Py_hash_t suffix;
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} djbx33a;
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struct {
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unsigned char padding[16];
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Py_hash_t hashsalt;
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} expat;
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} _Py_HashSecret_t;
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PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret;
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#endif
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#ifdef Py_DEBUG
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PyAPI_DATA(int) _Py_HashSecret_Initialized;
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#endif
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/* hash function definition */
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#ifndef Py_LIMITED_API
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typedef struct {
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Py_hash_t (*const hash)(const void *, Py_ssize_t);
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const char *name;
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const int hash_bits;
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const int seed_bits;
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} PyHash_FuncDef;
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PyAPI_FUNC(PyHash_FuncDef*) PyHash_GetFuncDef(void);
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#endif
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/* cutoff for small string DJBX33A optimization in range [1, cutoff).
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*
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* About 50% of the strings in a typical Python application are smaller than
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* 6 to 7 chars. However DJBX33A is vulnerable to hash collision attacks.
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* NEVER use DJBX33A for long strings!
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*
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* A Py_HASH_CUTOFF of 0 disables small string optimization. 32 bit platforms
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* should use a smaller cutoff because it is easier to create colliding
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* strings. A cutoff of 7 on 64bit platforms and 5 on 32bit platforms should
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* provide a decent safety margin.
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*/
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#ifndef Py_HASH_CUTOFF
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# define Py_HASH_CUTOFF 0
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#elif (Py_HASH_CUTOFF > 7 || Py_HASH_CUTOFF < 0)
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# error Py_HASH_CUTOFF must in range 0...7.
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#endif /* Py_HASH_CUTOFF */
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/* hash algorithm selection
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*
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* The values for Py_HASH_SIPHASH24 and Py_HASH_FNV are hard-coded in the
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* configure script.
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*
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* - FNV is available on all platforms and architectures.
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* - SIPHASH24 only works on platforms that don't require aligned memory for integers.
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* - With EXTERNAL embedders can provide an alternative implementation with::
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*
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* PyHash_FuncDef PyHash_Func = {...};
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*
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* XXX: Figure out __declspec() for extern PyHash_FuncDef.
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*/
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#define Py_HASH_EXTERNAL 0
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#define Py_HASH_SIPHASH24 1
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#define Py_HASH_FNV 2
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#ifndef Py_HASH_ALGORITHM
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# ifndef HAVE_ALIGNED_REQUIRED
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# define Py_HASH_ALGORITHM Py_HASH_SIPHASH24
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# else
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# define Py_HASH_ALGORITHM Py_HASH_FNV
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# endif /* uint64_t && uint32_t && aligned */
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#endif /* Py_HASH_ALGORITHM */
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_HASH_H */
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